This invention relates, in general, to microsensor devices, and in particular, to structures and methods for protecting microsensor devices exposed to harsh environments.
Microsensor devices are well known and have become key elements in process control and analytical measurement systems. Microsensor devices are used in many applications including industrial monitoring, factory automation, the automotive industry, transportation, telecommunications, computers and robotics, environmental monitoring, health care, and household appliances. Increasingly, microsensor devices are called upon to function reliably in harsh media including strong chemicals (e.g., polar and non-polar solvents, acid solutions, and alkaline solutions), extreme temperatures, and extreme pressures. Unless properly protected, these harsh environments can degrade or destroy microsensor performance.
Typically, in harsh media pressure sensor applications, the microsensor device is isolated from the harsh media using metal diaphragm/silicone oil transfer media techniques. This approach has several disadvantages including high cost, lower sensitivity, and impaired performance over temperature extremes. Other approaches include coating the pressure sensor device and the package containing the device with a conformal organic coating such as a polyparaxylylene coating (e.g., Parylene.RTM.). This approach has a disadvantage because organic coatings are limited as to the media conditions (e.g., composition, time, temperature extremes, pressure extremes) that a manufacturer can expose them to without damaging the underlying microsensor device.
As is readily apparent, structures and methods are needed for protecting microsensor devices from harsh media that can withstand a wide variety of media conditions, that are cost effective, and that have improved reliability.